HMRC Admin 10 Response

Hi
There is no rental income, as you parent's are paying your mortgage.  
If you sell the property, you may be subject to the equivalent of capital gains tax in Hong Kong.  
You would then convert the acquisition costs and the disposal value and costs to pounds sterling, to work out if there is a capital gain in the UK, if yes, the gain would be declared in a self assessment tax return.

Hi
Without knowing your financial/residential circumstances, we are unable to give you a definitive answer.
However, if the Self Assessment criteria tool indicates that you should complete a Self Assessment tax return, we would suggest that you do so.

Hi
Yes to both questions.

Hi
The interst paid on this investment is taxable as income.  
If you dispose of the asset for more that you paid for it, then the difference is capital gains.

Hi
You should report the total number of disposals on the tax return and a summary total for the disposal value and the acquisition costs for the year and include a breakdown of the disposal as a supplementary attachment.

Hi
Yes, the house price calculator you mention would be an acceptable source of market value information for Capital Gains tax calculation purposes.

Hi
You would answer yes to the question.
At the start of the Property page there are questions which asks if you are claiming Rent a Room relief.

Hi
Please note that your Capital Gains tax calculation should be based on your own personal circumstances, and on your 10% ownership share of the property.
HS283 Private Residence Relief (2021)                           
Tax when you sell property

Hi
If you have signed up for the Personal Tax Account you can update your estimated income for the employment.
You are correct regarding future contributions.

Hi
Please refer the to CG12440 guidance at (Location of assets) and S275 TCGA 1992.
If the third paragraph of CG12440 doesn’t give you the answer that you are looking for, you will need to write in to HMRC, with the full facts for their query to be forwarded to the relevant technical specialists. 
Taxation of Chargeable Gains Act 1992